package Day11;

import java.util.Scanner;

public class Test2 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int[] prices = new int[n];
            for(int i = 0;i < n;i++){
                prices[i] = in.nextInt();
            }
            int sum = 0;
            for(int right = 1,left = 0;right < n;right++){
                if(prices[right] > prices[left]){
                    sum += prices[right] - prices[left];
                    left = right;
                }else{
                    left = right;
                }
            }
            System.out.println(sum);
        }
    }
}
